1. Field of the Invention
The present invention relates to a printing system, formed of an information processing apparatus and an output apparatus for performing a printing operation in accordance with data supplied from the information processing apparatus. The invention also relates to a control method for the above type of printing system and to a medium on which a program implementing such a method is recorded.
2. Description of the Related Art
Hitherto, a printing system which is formed of a host apparatus, such as a personal computer, and a printer, between which two-way data communications are performed based on, for example, IEEE1284.4, is known. Above all, a printing system that controls data communications by informing the number of packets that can be transmitted and received between a host apparatus and a printer is also known. In the above type of printing system, the following two-way communication control has been suggested. A plurality of channels are provided in two-way communications: one of the channels is used for outputting print data, and the other channel is used for monitoring the current status of the printer. The number of packets that can be transmitted and received in each packet is informed between the host apparatus and the printer.
In the above-described communication control, however, after one apparatus has notified the other apparatus of the number of packets transmittable to the other apparatus, it requests the other apparatus to report the number of packets transmittable by the other apparatus, and is unable to perform data communications until it receives the answer. In this manner, one apparatus is required to request the other apparatus to inform the number of valid packets many times until it receives the answer. It is also necessary for the other apparatus to respond to the request by temporarily interrupting its current operation, which delays the operation which was to originally be performed. If the apparatus is required to make the request many times before receiving an answer, traffic is disadvantageously increased due to such wasteful requests.
In the event of printer errors, such as a paper jam or exhaustion of ink, the printer is unable to resume printing unless the factor causing the error is removed. Additionally, once the printer receives the maximum number of packets that it can receive, it is no longer able to receive more packets. Thus, any request made by the host apparatus to obtain the number of packets transmittable by the printer while an error is occurring wastefully increases traffic.
Accordingly, in view of the aforementioned problems, it is an object of the present invention to provide a printing system by which convenience of use and operation efficiency are improved and by which wasteful overheads caused by repeated issuing of a request for the number of valid packets are prevented, and also to a control method for the printing system and to a medium on which a program implementing the above control method is recorded.
In order to achieve the above object, according to one aspect of the present invention, there is provided a printing system comprising an information processing apparatus, and an output apparatus for performing a printing operation in accordance with data supplied from the information processing apparatus. The printing system comprises control means for controlling communications between the information processing apparatus and the output apparatus by checking a number of transmittable and receivable packets in each of communication channels provided between the information processing apparatus and the output apparatus. Adjusting means issues a request, after a lapse of a predetermined delay time, to instruct the output apparatus to notify the information processing apparatus of a number of valid packets of the output apparatus when there is no packet transmittable to the output apparatus from the information processing apparatus, and adjusts the delay time for issuing a subsequent request to the output apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the aforementioned printing system, the adjusting means may respond to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and may adjust the delay time for responding to a subsequent request from the information processing apparatus for the notification of the number of valid packets in accordance with the number of packets notified in response to the previous request.
In the aforementioned printing system, the adjusting means may issue a request, after a lapse of a predetermined delay time, to instruct the information processing apparatus to notify the output apparatus of a number of valid packets of the information processing apparatus in a case where there is no packet transmittable to the information processing apparatus from the output apparatus, and may adjust the delay time for issuing a subsequent request to the information processing apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the aforementioned printing system, the adjusting means may respond to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and may adjust the delay time for responding to a subsequent request from the output apparatus for the notification of the number of valid packets in accordance with the number of packets notified in response to the previous request.
According to another aspect of the present invention, there is provided a control method for a printing system which comprises an information processing apparatus and an output apparatus for performing a printing operation in accordance with data supplied from the information processing apparatus. The control method comprising the steps of: checking a number of transmittable and receivable packets in each of a plurality of communication channels provided between the information processing apparatus and the output apparatus; issuing a request, after a lapse of a predetermined delay time, to instruct the output apparatus to notify the information processing apparatus of a number of valid packets of the output apparatus when there is no packet transmittable to the output apparatus from the information processing apparatus; and adjusting the delay time for issuing a subsequent request to the output apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the aforementioned control method, the adjusting step may respond to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and may adjust the delay time for responding to a subsequent request from the information processing apparatus for the notification of the number of valid packets in accordance with the number of packets notified in response to the previous request.
In the aforementioned control method, the adjusting step may issue a request, after a lapse of a predetermined delay time, to instruct the information processing apparatus to notify the output apparatus of a number of valid packets of the information processing apparatus when there is no packet transmittable to the information processing apparatus. from the output apparatus, and the adjusting step may adjust the delay time for issuing a subsequent request to the information processing apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the foregoing control method, the adjusting step may respond to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and may adjust the delay time for responding to a subsequent request from the output apparatus for the notification of the number of valid packets in accordance with the number of packets notified in response to the previous request.
According to a further aspect of the present invention, there is provided a medium on which a program is recorded. The program comprises the steps of: checking a number of transmittable and receivable packets in each of a plurality of communication channels provided between an information processing apparatus and an output apparatus for performing a printing operation in accordance with data supplied from the information processing apparatus; issuing a request, after a lapse of a predetermined delay time, to instruct the output apparatus to notify the information processing apparatus of a number of valid packets of the output apparatus when there is no packet transmittable to the output apparatus from the information processing apparatus; and adjusting the delay time for issuing a subsequent request to the output apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the aforementioned medium, the program may comprise a step of responding to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and adjusting the delay time for responding to a subsequent request from the information processing apparatus for the notification of the number of valid packets in accordance with the number of packets obtained in response to the previous request.
In the aforementioned medium, the program may comprise a step of issuing a request, after a lapse of a predetermined delay time, to instruct the information processing apparatus to notify the output apparatus of a number of valid packets of the information processing apparatus when there is no packet transmittable to the information processing apparatus from the output apparatus, and adjusting the delay time for issuing a subsequent request to the information processing apparatus for the notification of the number of valid packets in accordance with the previous delay time and the number of packets obtained in response to the previous request.
In the aforementioned medium, the program may comprise a step of responding to the request for the notification of the number of valid packets after a lapse of a predetermined delay time, and adjusting the delay time for responding to a subsequent request from the output apparatus for the notification of the number of valid packets in accordance with the number of packets notified in response to the previous request.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.